Hi!

I would like to seek your kind advise and feedback on my regressions as I am not sure whether I am doing it correctly.

An introduction to my problem, I am looking to analyse the impact of COVID across different industries, for my data, I have 19 sub-sectors which encompasses 5 main sectors. I have generated a dummy year2020 to capture the COVID year.

I am using fe and have used:
Code:
xtset econsector
My first regression are as follow:
Code:
xtreg lnemp i.year i.quarter i.year2020##i.econsector, fe baselevels
note: 1.year2020 omitted because of collinearity
note: 2.econsector omitted because of collinearity
note: 3.econsector omitted because of collinearity
note: 4.econsector omitted because of collinearity
note: 5.econsector omitted because of collinearity
note: 6.econsector omitted because of collinearity
note: 7.econsector omitted because of collinearity
note: 8.econsector omitted because of collinearity
note: 9.econsector omitted because of collinearity
note: 10.econsector omitted because of collinearity
note: 11.econsector omitted because of collinearity
note: 12.econsector omitted because of collinearity
note: 13.econsector omitted because of collinearity
note: 14.econsector omitted because of collinearity
note: 15.econsector omitted because of collinearity
note: 16.econsector omitted because of collinearity
note: 17.econsector omitted because of collinearity
note: 18.econsector omitted because of collinearity
note: 19.econsector omitted because of collinearity

Fixed-effects (within) regression               Number of obs     =        456
Group variable: econsector                      Number of groups  =         19

R-sq:                                           Obs per group:
     within  = 0.4989                                         min =         24
     between = 0.0978                                         avg =       24.0
     overall = 0.0110                                         max =         24

                                                F(26,411)         =      15.74
corr(u_i, Xb)  = 0.0763                         Prob > F          =     0.0000

-------------------------------------------------------------------------------------------------------------------------------------------
                                                                    lnemp |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
--------------------------------------------------------------------------+----------------------------------------------------------------
                                                                     year |
                                                                    2015  |          0  (base)
                                                                    2016  |    .003923   .0058952     0.67   0.506    -.0076654    .0155115
                                                                    2017  |   .0270333   .0058952     4.59   0.000     .0154448    .0386217
                                                                    2018  |   .0488873   .0058952     8.29   0.000     .0372988    .0604757
                                                                    2019  |   .0708191   .0058952    12.01   0.000     .0592307    .0824076
                                                                    2020  |   .0437246   .0202506     2.16   0.031      .003917    .0835323
                                                                          |
                                                                  quarter |
                                                                       1  |          0  (base)
                                                                       2  |  -.0064956   .0048134    -1.35   0.178    -.0159576    .0029663
                                                                       3  |    .000597   .0048134     0.12   0.901    -.0088649    .0100589
                                                                       4  |   .0109844   .0048134     2.28   0.023     .0015224    .0204463
                                                                          |
                                                                 year2020 |
                                                                       0  |          0  (base)
                                                                       1  |          0  (omitted)
                                                                          |
                                                               econsector |
                                                             Agriculture  |          0  (base)
                                          Beverages and tobacco products  |          0  (omitted)
                                                            Construction  |          0  (omitted)
                             Electrical, electronic and optical products  |          0  (omitted)
                                                   Finance and insurance  |          0  (omitted)
                                      Food & beverages and accommodation  |          0  (omitted)
                                           Information and communication  |          0  (omitted)
                                                    Mining and quarrying  |          0  (omitted)
Non-metallic mineral products, basic metal and fabricated metal products  |          0  (omitted)
                                                          Other Services  |          0  (omitted)
                        Petroleum, chemical, rubber and plastic products  |          0  (omitted)
                                       Real estate and business services  |          0  (omitted)
                          Textiles, wearing apparel and leather products  |          0  (omitted)
                     Transport equipment, other manufacturing and repair  |          0  (omitted)
                                              Transportation and storage  |          0  (omitted)
                                                               Utilities  |          0  (omitted)
                    Vegetable and animal oils & fats and food processing  |          0  (omitted)
                                              Wholesale and retail trade  |          0  (omitted)
                   Wood products, furniture, paper products and printing  |          0  (omitted)
                                                                          |
                                                      year2020#econsector |
                                        1#Beverages and tobacco products  |  -.0538645   .0281491    -1.91   0.056    -.1091986    .0014696
                                                          1#Construction  |  -.0813015   .0281491    -2.89   0.004    -.1366356   -.0259673
                           1#Electrical, electronic and optical products  |   .0318838   .0281491     1.13   0.258    -.0234504    .0872179
                                                 1#Finance and insurance  |   .0284702   .0281491     1.01   0.312    -.0268639    .0838044
                                    1#Food & beverages and accommodation  |   .1063291   .0281491     3.78   0.000      .050995    .1616632
                                         1#Information and communication  |   .1041067   .0281491     3.70   0.000     .0487726    .1594408
                                                  1#Mining and quarrying  |  -.0607854   .0281491    -2.16   0.031    -.1161196   -.0054513
                                                                       1 #|
Non-metallic mineral products, basic metal and fabricated metal products  |   .0315135   .0281491     1.12   0.264    -.0238207    .0868476
                                                        1#Other Services  |  -.0031687   .0281491    -0.11   0.910    -.0585028    .0521655
                      1#Petroleum, chemical, rubber and plastic products  |    .038587   .0281491     1.37   0.171    -.0167472    .0939211
                                     1#Real estate and business services  |   .0623288   .0281491     2.21   0.027     .0069947    .1176629
                        1#Textiles, wearing apparel and leather products  |   .0594772   .0281491     2.11   0.035     .0041431    .1148113
                   1#Transport equipment, other manufacturing and repair  |   -.042689   .0281491    -1.52   0.130    -.0980231    .0126451
                                            1#Transportation and storage  |   .0281065   .0281491     1.00   0.319    -.0272276    .0834406
                                                             1#Utilities  |   .0254008   .0281491     0.90   0.367    -.0299334    .0807349
                  1#Vegetable and animal oils & fats and food processing  |    .062471   .0281491     2.22   0.027     .0071369    .1178051
                                            1#Wholesale and retail trade  |   .0717998   .0281491     2.55   0.011     .0164657     .127134
                 1#Wood products, furniture, paper products and printing  |  -.0374862   .0281491    -1.33   0.184    -.0928203    .0178479
                                                                          |
                                                                    _cons |   6.002973   .0051054  1175.82   0.000     5.992937    6.013009
--------------------------------------------------------------------------+----------------------------------------------------------------
                                                                  sigma_u |  1.2651704
                                                                  sigma_e |   .0363403
                                                                      rho |  .99917563   (fraction of variance due to u_i)
-------------------------------------------------------------------------------------------------------------------------------------------
F test that all u_i=0: F(18, 411) = 24241.02                 Prob > F = 0.0000
However, when I ran this, the sector agriculture was used as based. But I also want to understand the impact of this sector. Hence, I have generated main sector dummies such as manufacturing which consist of 7 subsectors as below:

Code:
gen manuc = 0
replace manuc = 1 if econsector == 17 | econsector == 2 | econsector == 13 | econsector == 19 | econsector == 11 | econsector == 9 | econsector == 4 | econsector == 14
label var manuc "Manufacturing Sector"
And I have regress and obtained below:

Code:
xtreg lnemp i.year i.year2020##manuc, fe allbaselevels
note: 1.year2020 omitted because of collinearity
note: 1.manuc omitted because of collinearity

Fixed-effects (within) regression               Number of obs     =        456
Group variable: econsector                      Number of groups  =         19

R-sq:                                           Obs per group:
     within  = 0.3205                                         min =         24
     between = 0.1706                                         avg =       24.0
     overall = 0.0016                                         max =         24

                                                F(6,431)          =      33.88
corr(u_i, Xb)  = 0.0176                         Prob > F          =     0.0000

--------------------------------------------------------------------------------
         lnemp |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
---------------+----------------------------------------------------------------
          year |
         2015  |          0  (base)
         2016  |    .003923   .0067036     0.59   0.559    -.0092529    .0170989
         2017  |   .0270333   .0067036     4.03   0.000     .0138574    .0402092
         2018  |   .0488873   .0067036     7.29   0.000     .0357114    .0620631
         2019  |   .0708191   .0067036    10.56   0.000     .0576433     .083995
         2020  |   .0692961   .0080342     8.63   0.000      .053505    .0850872
               |
      year2020 |
            0  |          0  (base)
            1  |          0  (omitted)
               |
         manuc |
            0  |          0  (base)
            1  |          0  (omitted)
               |
year2020#manuc |
          0 0  |          0  (base)
          0 1  |          0  (base)
          1 0  |          0  (base)
          1 1  |  -.0143349   .0105172    -1.36   0.174    -.0350062    .0063364
               |
         _cons |   6.004244   .0047402  1266.67   0.000     5.994928    6.013561
---------------+----------------------------------------------------------------
       sigma_u |  1.2674848
       sigma_e |    .041324
           rho |  .99893816   (fraction of variance due to u_i)
--------------------------------------------------------------------------------
F test that all u_i=0: F(18, 431) = 21938.97                 Prob > F = 0.0000
I am planning to regress for the other 4 main sector and compare the interaction coefficient between the main sectors (ie. (1)(1) = -.014.)

Do you think the second regression is feasible? or I should just use the first regression. Appreciate further comments on this.

Thank you!